A number not divisible by 2 is called an odd number. Any number whose unit digit(last digit) is either 1,3,5,7 or 9 is an odd number.

The set of all odd numbers is represented as

Odd numbers = { 2n+1: n ∈  Z } where Z is the set of all integers.

• When an even number is subtracted from an odd number, it results in an odd number.
• When two odd numbers are subtracted, it results in an even number.